As drills used in cut processing of a work material such as a metal member, there have been conventionally known the drills disclosed in Japanese Unexamined Patent Application Publication No. 2007-307642A (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2012-110984A (Patent Document 2). The drills disclosed in Patent Documents 1 and 2 include a body, two cutting edges formed at a tip end of the body, and two twisted flutes for discharging chips generated by the cutting edges. The two flutes have helix angles that differ from each other. The difference between the helix angle of one flute and the helix angle of the other flute causes the two flutes to join at a position receded by a predetermined amount from the tip end of the body, forming one flute rearward from a joining point. The joining of the two flutes makes it possible to increase a rigidity on a rear portion side of the body while performing machining with a favorable cutting balance.
In the drills disclosed in Patent Documents 1 and 2, the direction in which the chips flow changes at a location where the two flutes join. Nevertheless, because the two flutes directly join, a space through which the chips flow at the location where the flutes join is not sufficiently wide, resulting in the possibility of chip flow stagnation and clogged by chips.
The present invention has been made in view of the above problems, and it is an object of the present invention to provide a drill capable of favorably discharging chips even if the drill includes a plurality of joining flutes.